Foam in bag packaging system and method for producing the same

ABSTRACT

A packaging system for producing a foam-in-bag cushion upon demand includes a bag of flexible plastic film and defining therein an enclosed space which is vented to the outside of the bag, a foam precursor packet positioned at a predetermined location within the enclosed space in the bag and being formed of a barrier material. The packet includes first and second compartments with a first frangible seal separating the first and second compartments which when ruptured will permit the contents of the compartments to be mixed to form a foam cushion and a second frangible seal between one of the compartments and the enclosed space in the bag. A first foam precursor component is contained in the first compartment of the packet and a second foam precursor component is contained in the second compartment of the packet. The frangible seals have a peel strength of at least about one pound per inch and less than about twelve pounds per inch and more particularly a peel strength of about one pound per inch to about seven pounds per inch. The frangible seals are formed by providing bands of printed area on the facing surfaces of the material forming the packet which is arranged in a matrix of printed and unprinted areas. The printed areas prevent the surfaces from being joined by heat sealing and the matrix is such that a frangible seal of the desired peel strength is formed.

This application is a continuation application under 35 U.S.C. § 120 ofprior U.S. patent application Ser. No. 09/914,824 filed May 14, 2002Betram et al for “Foam in Bag Packaging System and Method for Producingthe Same” (parent application), now U.S. Pat. No. 6,712,201 which is theNational Stage (35 U.S.C. § 371) of International Application No.PCT/US99/05724 filed Mar. 12, 1999, which claims the benefit of U.S.Provisional Application No. 60/077,962 filed Mar. 13, 1998. Each of theapplications listed in the previous sentence is incorporated herein inits entirety by reference.

FIELD OF THE INVENTION

The present invention relates to foam-in-place packaging of articlessusceptible to damage during handling, shipment and storage and inparticular, relates to foam-in-bag packaging systems which will producefoam cushions upon demand and a method of producing the same.

BACKGROUND OF THE INVENTION

The packaging of fragile articles or articles susceptible to damageduring such packaging, shipment and storage presents many distinctproblems. Foam-in-place packaging has been well known and widely used asprotective packaging for such articles for a number of years.Foam-in-place technology is based upon the reaction between two (usuallyliquid) precursor components, which when mixed will react to form apolymer foam and gaseous by-products. In particular, and most commonly,an isocyanate containing component is mixed with a polyol containingcomponent and these components react to produce a urethane polymer(polyurethane), steam and carbon dioxide. Under proper conditions, thesteam and carbon dioxide generated by the reaction will disburse throughthe polymer and form an expanded polyurethane foam that providesprotective cushioning for articles being packaged. The reaction of thecomponents, when mixed to form an expanded foam, takes a minute or twoand this time frame makes it feasible to manipulate and use the foam forpackaging purposes. Initially, the foam precursor components wereinjected into containers (e.g. corrugated boxes), and either a moldelement was used to form an article receiving cavity as the foamexpanded or the article wrapped in a protective material was itselfplaced in the container and the foam permitted to expand therearound.Such foam-in-place packaging has been very successful and is stillwidely used for certain packaging purposes. However, such foam-in-placepackaging did not address or was not suited for many packaging purposes.

Accordingly, a next generation of foam-in-place packaging has beendeveloped in which devices were provided which concurrently form plasticbags and inject into the bag the mixture of foam precursor components.This bag is provided with vents to the outside to-permit the steam andcarbon dioxide by-products to escape during the formation of the foam.Prior to the reaction of the components to produce foam, an operatorplaces the newly made bag into a container in which an object has beenplaced and then closes the container. The precursors react to producefoam which fills the void areas within the container, while forming acustom shaped cushion around the object being packaged. Such foam-in-bagpackaging technology has also been quite successful and is now insubstantial use.

Examples of such foam-in-bag technology heretofore developed is shownand described in a number of patents commonly assigned with thisapplication and including U.S. Pat. Nos. 4,800,708; 4,854,109;4,938,007; 5,027,583; 5,139,151 and 5,376,219.

All of these devices are characterized by forming the bags and injectingthe foam precursor components into the bags immediately prior to thereaction of the components and the production of foam in the bags.Therefore, these devices by necessity must be placed adjacent thepackaging operation. Here again, these devices are not adaptable orusable in all packaging situations, although they have greatly expandedthe use of foam-in-place packaging technology.

U.S. Pat. No. 5,699,902, also commonly assigned to the Assignee of thisapplication, discloses a still further generation of foam-in-placepackaging. This patent discloses a packaging system in which a bag isformed of flexible plastic film material defining an enclosed spacetherein and having separate interior cells in the enclosed space. Thecells contain two different foam precursor components. The two cellscontaining the foam precursor components are separated by a frangibleseal which maintains the precursor components separate until it isdesired to use the bag. Once the packaging system is to be used, thefrangible seal between the two cells is broken and the two precursorcomponents are mixed.

There is also provided another frangible seal between the cells and theenclosed space within the bag. This second frangible seal is broken bythe reaction of the two precursor components and the production of foamwhich expands out of the cells into the enclosed space in the bag untilthe interior of the bag is substantially filled and a foam cushion isformed. The interior of the bag is vented to the outside so that thegaseous by-products of the foaming reaction may escape from the bag. Bythis arrangement, a foam-in-bag packaging system has been provided inwhich bags could be produced at locations remote from the packagingoperations, packaged in containers, shipped to the packaging operationlocations and stored until desired for use. When desired for use, anappropriately sized bag is removed from its container, the firstfrangible seal between the two cells is broken and the chemicals mixed,and the second frangible seal is broken by the reaction and a foamcushion is formed in the enclosed space in the bag. Accordingly, apackaging system of greatly increased versatility and usability was thusprovided. However, the production of reliable frangible seals whichmaintain the two components separate, but which may be readily fracturedto permit mixing of the components has been the cause of concern andanxiety.

SUMMARY OF THE INVENTION

With the foregoing in mind, it is an object of the present invention toprovide flexible packages having a unique frangible seal which maintainsprecursor components separate while being readily fracturable upondesired use of the package to provide mixing of the heretofore separatedcomponents.

The foregoing object of this invention is achieved by providing a bagformed of flexible plastic material which defines an interior enclosedspace, which interior space is vented to the outside of the bag topermit gaseous by-products of the foaming reaction to escape. A packetor pouch having a plurality of compartments therein, separated from eachother by at least one frangible seal and having another frangible sealbetween the compartments in the packet and the enclosed space within thebag, is provided within the bag. First and second foam precursorcomponents are contained in the separate compartments within the packetand are maintained separated by the interior frangible seal. The packetis formed of a barrier material which is capable of maintaining the foamprecursors in a substantially stable and unreacted state for the desiredshelf life of the foam-in-bag packaging system.

A packaging system of this type is disclosed in the co-pendingapplication, Ser. No. 09/042,444 filed Mar. 13, 1998 entitled “Foam InBag Packaging System and Method For Producing the Same,” whichapplication is commonly assigned to the Assignee of this application andis incorporated herein by reference.

In accordance with a first preferred embodiment, the frangible seals ofthis invention, include a seal pattern which comprises one or moresubstantially continuous seal lines, each of which extend substantiallybetween opposite sides of the packet to substantially divide the packetinto a plurality of compartments. Each seal line is configured such thatany imaginary straight line between the opposite sides of the packet andintersecting the seal line subtends at least one converging pocketdefined by two segments of the seal lines which converge upon each otherin the opening direction. Accordingly, the converging seal line segmentsare at oblique angles to the first direction. Preferably, this seal linedefines a plurality of converging pockets which are spaced apart andextend substantially from one side of the compartment of the packet tothe other. Thus, when the compartment is compressed, it causes liquid inthe compartment to advance in the second direction, the leading edge orfront of the liquid intersects a given seal line and liquid enters thewide end of each of the converging pockets and flows to the narrow endthereof. Fluid forces acting outwardly on the opposing panels which arejoined along the converging seal line segments accordingly causeprogressive peeling apart of the barrier material in the region of eachconverging pocket from the wide end toward the narrow end thereof.

By way of example and not by way of limitation, seal patterns inaccordance with the first preferred embodiment of the invention includegrids of spaced-apart intersecting seal lines in orthogonal ornon-orthogonal fashion running oblique to the first direction andextending to each of the opposite sides of the packet, such that seallines extending from one side to the other are defined by joinedsegments of the grid lines. Alternatively, the seal pattern may comprisewave form seal lines, such as saw-tooth or wavy lines extending from oneside to the other. The converging pockets may take a variety of forms,including but not limited to triangular or V-shaped, cusp-shaped,U-shaped or other shapes.

In accordance with a second preferred embodiment of the invention, theseal pattern comprises a plurality of discrete sealed areas separatedfrom one another by unsealed areas and arranged in a regular matrixhaving a density of at least about 15 matrix lines per inch, and morepreferably at least about 50 matrix lines per inch.

A frangible seal in accordance with the invention may be formed byvarious techniques. In a preferred method, the opposing panels ofbarrier material have inner surfaces that are heat sealable to eachother. One of the opposing regions of the inner surfaces that are to bejoined to create the frangible seal is covered by a layer of resistmaterial which prevents the heat sealing of the opposing surfaces toeach other. The resist material is applied in a reverse image of theseal pattern. For example, to produce a square grid seal pattern, resistmaterial is applied in a checker board pattern with the squares ofresist material spaced apart such that the spaces between the squaresdefine intersecting or orthogonal lines along which the panels ofbarrier material are to be joined.

The opposing panels of barrier material are overlayed with their innersurfaces confronting each other. The panels are pressed together andheat and pressure are then applied to the panels in a region of theresist material to cause heat sealing of the panels together in theareas not covered by the resist material.

The resist material may be applied by various techniques. In a preferredmethod, a resist material is printed onto the inner surface of one ofthe panels by a rotary printing press, such as a flexographic,roto-gravure or rotary letterbox press. Where the frangible seal isformed by a matrix of sealed areas, the seal advantageously is formed byprinting resist material onto the inner surface of one of the panels bya half-tone printing process. The resist is applied with a half-tone dotline density of at least about 15 lines per inch and a surface coverageof at least about 60%.

The resist material may comprise a material having an acrylic/styreneresin-based vehicle, and other components, such as surfactants, alcohol,defoamers, and waxes may be added to the vehicle to improve adhesion,wetting out, and other properties of the resist for insuring accurateapplication of the resist pattern to the panel surface. A pigment may beadded to the vehicle to facilitate visual inspection of the resistpattern. Also, solvent based inks, such as nitro-cellulose, polyamidetype inks, may be used.

In accordance with one preferred embodiment of the invention, the innersurfaces of the panels are formed of a substantially non-polar polymermaterial which has not been treated by chemical modification, such ascorona discharge treatment or flame treatment or by other treatments, toimpair to any significant degree the strength of the non-frangible bestseals. The panels are thus more readily heat sealable to each other sothat sufficiently strong non-frangible seals may be achieved to formfluid-tight compartments in a packet. The invention also providespackets incorporating one or more frangible seals in accordance with theinvention. In accordance with a preferred embodiment of the invention, apacket is provided having two compartments for containing two differentcomponents, the compartments being separated by a frangible sealaccording to the invention. Preferably, the packet also includes asecond frangible seal between one of the compartments and the outsidewhich, once the packet is placed in the bag, will comprise the interiorspace within the bag. Advantageously, the second frangible seal has agreater peel strength than the first frangible seal so that the secondseal is not inadvertently ruptured when the user compresses one of thecompartments to break the first seal, thus assuring that the tworeactive fluids are brought into intimate contact within the package sothat thorough mixing occurs before either fluid can escape the packet.

A further preferred embodiment of a packet for containing foam-formingprecursors includes panels formed of a laminate having, from an outerlayer to an inner layer thereof, an oriented polyethylene teraphthalatelayer, a polyethylene tie layer, a metal foil layer, an ethylene acrylicacid layer and a non-polar polymer layer, such as low densitypolyethylene, linear low-density polyethylene, or the like.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the inventionwill become more apparent from the following description of certainpreferred embodiments thereof, when taken in conjunction with theaccompanying drawings in which,

FIG. 1 is a plan view of a foam-in-bag packaging system in accordancewith the present invention;

FIG. 2 is a fragmentary enlarged plan view of the bag shown in FIG. 1illustrating the manner of fracturing or rupturing the interiorfrangible seal and mixing of the foam precursor components within thepacket;

FIG. 3 is an enlarged fragmentary sectional view taken substantiallyalong line 3—3 in FIG. 1;

FIG. 4 is a plan view of a packet in accordance with one preferredembodiment of the present invention having an inner frangible sealbetween two compartments and an outer frangible seal for releasing thefoam precursors from the packet;

FIG. 5 is a plan view of a sheet of flexible barrier material from whichthe packet illustrated in FIGS. 1–4 is formed and illustrating the innersurface having two areas of resist material applied for formation of thetwo frangible seals;

FIG. 6 is an enlarged fragmentary view of a portion of the seal patternfor the inner frangible seal as illustrated in FIG. 5;

FIG. 7 is a cross-sectional view taken substantially along line 7—7 ofFIG. 4;

FIG. 8 is an enlarged fragmentary view of a portion of the innerfrangible seal shown in FIG. 7;

FIG. 9 is a fragmentary schematic view illustrating an alternate sealpattern for forming the frangible seals of the packet of the presentinvention;

FIG. 10 is a fragmentary schematic view depicting another alternativeseal pattern for forming the frangible seals of the packet of thisinvention;

FIG. 11 is a fragmentary schematic view depicting yet anotheralternative seal pattern for forming the frangible seals;

FIG. 12 is a fragmentary schematic view depicting a still furtheralternative seal pattern for forming the frangible seals of the packetof this invention;

FIG. 13 is a fragmentary schematic view depicting a half-tone sealpattern for forming the frangible seals of the present invention;

FIG. 14 is a schematic view of a printing apparatus for applying aresist material to a web of barrier material for forming packets inaccordance with this invention; and

FIG. 15 is a fragmentary enlarged cross-sectional view takensubstantially along line 15—15 in FIG. 4.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Referring now more specifically to the drawings and particularly to FIG.1, there is illustrated therein a foam-in-bag packaging system generallyindicated at 30, incorporating the features of the present invention.The packaging system 30 includes a bag, generally indicated at 31, whichincludes a pair of superposed panels 32 and 33. Panels 32 and 33 areformed of flexible plastic film material, such as that described in U.S.Pat. No. 5,699,902 issued Dec. 23, 1997, which is incorporated fullyherein by reference. Panels 32 and 33 are preferably elongate and havesides 35, 36 and ends 37, 38 joined together to define an enclosed space34 therewithin. It is to be understood that panels 32 and 33 may beformed from separate sheets of plastic film material or, as illustrated,from a single sheet or web of plastic film material folded along itslongitudinal center line to form the joined side edge 35. The other sideedge 36 and the end edges 37 and 38 are joined together by heat seals 36a, 37 a and 38 a to enclose completely the space 34 between the panels32 and 33. The enclosed space 34 is vented to the outside of the bag 31by a band 39 of perforations through at least one of the panels 32 and33.

A packet or pouch 40 is positioned within the space 34 between thepanels 32 and 33 prior to the joinder of the side and end edges 36 and37, 38. Preferably packet 40 is positioned adjacent one end of the bag31, but it is to be understood that the packet 40 may be located at anydesired location within the enclosed space 34. Most preferably, packet40 is positioned at the opposite end of bag 31 from the band 39 ofventing perforations and is secured in this position in a suitablemanner, such as by an adhesive.

Packet 40 includes a pair of panels 41 and 42 of a barrier materialcapable of maintaining foam precursor compositions in a stable,unreacted state for as long as required between manufacture thereof anduse of the foam-in-bag packaging system 30. This barrier materialpreferably is a composite material which includes a heat sealable layeron the inside surface of the barrier material when the barrier materialis formed into the packet 40 and other layers of material necessary toprovide the requisite moisture imperviousness and other barriercharacteristics. Such a composite material is described in U.S. Pat. No.5,699,902 which has been incorporated herein by reference.

The panels 41 and 42 may be formed from separate sheets of barriermaterial or may be formed by a single sheet of barrier material that isfolded longitudinally along the center line thereof as described above.Prior to formation of the panels 41 and 42 into the packet 40, certainareas of panel 41 are printed with a release or masking material or inkto prevent areas covered thereby from being heat sealed to panel 42. Inthis embodiment, a first printed area 43 extends transversely of thewidth of panel 41 from a point near the longitudinal fold line towardthe outer side edge thereof, a predetermined distance less than the fallwidth of panel 41. A second printed area 44 extends longitudinally ofpanel 41 from a point spaced from the right end (FIG. 5) toward the leftend, a predetermined distance which may extend to the printed area 43.The printed areas 43 and 44 comprise discontinuous printed patterns withspaced apart printed areas 43 a and 44 a leaving unprinted areas 43 band 44 b therebetween. Since printed areas 43 a and 44 a serve asmasking for the underlying heat sealable layer and prevent the panels 41and 42 from being heat sealed together wherever a printed area 43 a or44 a occurs, only unprinted areas 43 b and 44 b may be heat sealed topanel 42, thereby forming frangible seals.

It is important that the second printed area 44 of the resist patternextend completely to the side edge of the panel 41 of barrier material,as any region of the panel not covered by the printed pattern 44 alongthat edge tends to form a seal along the edge that is difficult torupture. Accordingly, it is advantageous to form the panel 41 slightlywider than its finished size and to extend the resist pattern 44 into amarginal edge region which is subsequently cut off along a cut line thatgoes through the resist pattern 44, thus assuring that there is no stripof uncovered sheet material at the edge in the region of the resistpattern 44.

The resist material printed on printed areas 43 and 44 may be of amaterial having an acrylic/styrene resin-based vehicle, and othercomponents such as surfactants, alcohols, defoamers and waxes which maybe added to the vehicle to improve adhesion, wetting out, and otherproperties of the resist for ensuring accurate application of the resistpatterns to the innersurface of panel 41. A pigment may be added to thevehicle to facilitate visual inspection of the resist pattern. Also,solvent based inks, such as nitro-cellulose, polyamide type inks, may beused. The resist material is also referred to herein as an ink, althoughthe invention is not limited to ink for the resist material.

The resist material may be applied by various techniques. In a preferredmethod in accordance with the invention, the resist material is printedonto the inner surface of the panel 41 in a rotary printing press, suchas a flexographic, roto-gravure or rotary letterbox press. For example,FIG. 14 schematically depicts a printing apparatus 100 for printingresist onto a roll of material for forming the panels 41 and 42. Theapparatus 100 includes an ink fountain 101, a fountain roll 102 whichpicks up ink from the ink fountain 101, an engraved transfer roll 103(also known as an Anilox roll) which transfers ink from the fountainroll to a plate cylinder 104. The plate cylinder 104 has a flexibleplate 105 wrapped thereabout, the plate 105 having raised areas 106 towhich ink is adhered. The web of sheet material is passed through thenip defined between the plate cylinder 104 and an impression cylinder108 which applies pressure to the web to permit transfer of ink from theraised areas onto the surface of the web.

Formation of the packet 40 may be performed on a packaging machine whichmanipulates the elongated printed web 120 by c-folding the web and heatsealing the web to form the permanent and frangible seals. However, theinvention is not limited to any particular technique for forming thepacket 40 and those skilled in the art will readily comprehend othersuitable techniques for forming packets 40 in accordance with thepresent invention.

The panels 41 and 42 are folded along the longitudinal center line ofthe sheet of barrier material to position panels 41 and 42 in juxtaposedrelation. The side and end edges of the panels 41 and 42 are joined toprovide an enclosed space between panels 41 and 42. One side edge isjoined by the fold 45. The opposite side edges of panels 41 and 42 areheat sealed together by a heat seal 46 and the ends are similarly heatsealed together by heat seals 47 and 48. A heat seal 49 extendstransversely across the panels 41 and 42 intermediate the printed area43 such that heat seal 49 includes a frangible seal 49 a within theprinted area 43. Seal 49 divides the enclosed space between panels 41and 42 into first and second compartments 50 and 51. Compartment 50 isfilled with a first foam precursor component 52 and compartment 51 isfilled with a second foam precursor component 53. Preferably, the firstfoam precursor component 52 is an isocyanate containing component andthe second foam precursor component 53 is a polyal containing component.The heat seal 46 extends along the length of printed area 44 and, inthat area, provides a second frangible seal 46 a between the secondcompartment 51 and the enclosed space 34 in bag 31. To ensure that-thefrangible seals 49 a and 46 a are sufficiently frangible, that the samecan be broken as needed and break evenly and smoothly, it is preferredthat the transverse frangible seal 49 a should have a peel strength ofabout 0.5 to about 3.5 pounds per inch and that frangible seal 46 a havea peel strength of 6–7 pounds per inch or less. The peel strength isdetermined by a peel test performed on an Instron machine. This peeltest essentially comprises pulling apart two sealed sheets in oppositedirections at 90° to the plane of the peeled sheets and measuring theforce required to peel the sheets apart per inch of sheet width measuredalong the line along which the sheets separate. By way of comparison,the heat seals 46, 47, 48 and 49 in areas other than the printed areas43 and 44 have a peel strength of about 12 to about 20 pounds per inch.

A peel strength of the level preferred for the frangible seal 49 a issuitable for allowing rupturing of the inner frangible seal 49 a whenrelatively moderate compression is applied to either of the compartments50 or 51. Upon rupture of the frangible seal 49 a, the foam precursorcomponents in the compartments 50 and 51 can mix since the rupture ofthe frangible seal 49 a transforms the separate compartments into asingle joined compartment. Thorough mixing of the two precursorcomponents may be accomplished by kneading the packet 40 in alternationto cause a back and forth flow of the combined components within thepacket, as is illustrated in FIG. 2.

The outer frangible seal 46 a is for dispensing or releasing the mixedcomponents from the packet 40 into the enclosed space 34 of bag 31 uponthe commencement of a foaming reaction. The outer seal 46 aadvantageously has a peel strength which is greater than that of theinner frangible seal 49 a, but less than that of the permanent sealsalong the edges and ends of the packet 40. Thus, the compression of thecomponents in one of the compartments to rupture the inner frangibleseal 49 a does not rupture the outer frangible seal 46 a so that thecomponents are confined within the packet 40 until foaming reactioncommences.

The inner and outer frangible seals 49 a and 46 a may be formed in anysuitable manner which provides the desired degree of peel strength.However, it has been found particularly advantageous to construct thesefrangible seals in the manner to be described below so as to ensure thatuniform seals strengths are obtained, and repeatable and controlledrupturings of the seal are achieved.

To these ends, a frangible seal in accordance with this invention isformed by sealing together the opposed panels 41 and 42 of the packet 40with a seal pattern which leaves a majority of the panels' surface areasunsealed in the region of the frangible seals 49 a or 46 a, and whereinthe sealed areas define a pattern having certain characteristics.

The seal pattern may be formed by various techniques. For example, wherethe patterns are heat sealable to each other, the seal pattern may beproduced by configuring the heat sealing dyes or jaws with the desiredpattern. However, it has been found advantageous to form the frangibleseal pattern by applying the resist material to the inner heat sealablesurface of one of the opposing panels, which are to be joined to formthe seal. The resist material is applied in a reverse or negative imageof the desired seal pattern. The resist material prevents heat sealingof the panels 41 and 42, and accordingly the desired seal pattern isobtained by applying pressure and heat to the panels in a region of theresist material, which causes the panels to be sealed together whereverresist material is absent.

The resist patterns 43 and 44 are configured, in the embodiment of theinvention depicted in FIG. 5, as squares 43 a and 44 a arranged in acheckerboard fashion, such that the regions of the panel 41 not coveredby the resist material, form an orthogonal grid of intersecting lines 43b and 44 b. It will be appreciated that the resultant seal patternformed by heat sealing the opposing panels 41 and 42 along the region ofthe resist pattern 43 will comprise seal lines forming an orthogonalgrid of intersecting lines substantially identical to the lines 43 b.Thus, the resist pattern 43 is a reverse or negative image of thedesired sealed pattern, and accordingly, the lines 43 b are referred toherein as seal lines.

The seal pattern is configured to facilitate a uniform and controlledpeeling apart of the opposing panels 41 and 42 of the packet 40 when oneof the compartments 50 or 51 is compressed to cause rupturing of theinner frangible seal 49 a. This is achieved by arranging the sealpattern such that a linear front of fluid, represented by the line 60 inFIG. 6, which is advancing from compartment 51 toward compartment 50along a direction generally perpendicular to the inner frangible seal 49a and encounters at least one converging pocket 61 (FIG. 6) defined by asegment of seal lines 43 b which are at oblique angles to the advancingfluid front along the line 60. Preferably, there are a plurality ofconverging pockets 61 spaced apart along the seal line between theopposite ends of the frangible seal 49 a, as is shown in FIG. 6. Theconverging pockets 61 facilitate peeling apart of the opposing panels 41and 42 of the packet 40 by fluid pressure acting within the pockets 61,which causes the panels 41 and 42 to be peeled apart along thedirections of the oblique converging seal lines of the pockets 61, suchas seal lines 62 (FIG. 6).

The seal lines 43 b advantageously have a width of about 0.002 inch toabout 0.01 inch, and more preferably about 0.002 inch to about 0.006inch. The grid patterns 43 and 44 may be tailored to achieve desiredseal strength. For instance, to facilitate making the outer frangibleseal 46 a stronger than the inner frangible seal 49 a, the seal lines inthe inner resist pattern 43 preferably are 0.003 inch wide and the seallines 44 b in the outer pattern 44 are 0.004 to 0.005 inch wide.Further, the grid in the inner resist pattern 43 may have a differentgrid size or spacing between seal lines than that of the outer resistpattern 44. The inner and outer resist patterns 43 and 44 advantageouslyhave a grid spacing of about 0.08 inch to about 0.11 inch.

It has been found that if the points of intersection of the orthogonalseal lines 43 b and 44 b are aligned along the direction of the fluidfront, rupturing of the frangible seal 49 a and 46 a is not uniform andtends to occur in a irregular or jerky fashion as the aligned innersection points all tend to become unsealed at about the same moment, andthis repeats for each row of aligned intersection points. It has furtherbeen discovered that this non-uniform or irregular opening is alleviatedappreciably by orienting the grid such that the intersection pointsdefine an oblique line at an angle α with respect to the fluid frontdirection represented by line 60. The angle α is preferably about 5° toabout 9° and more preferably about 7°.

As is illustrated in FIGS. 7 and 8, the inner frangible seal 49 a of thepacket 40 preferably comprises two discreet seals 49 a ₁ and 49 a ₂separated by an unsealed region therebetween. This facilitates formingthe packet 40 on a packaging machine in which two heat sealing bars areused alternately to form the two seals 49 a ₁ and 49 a ₂ of twocontiguous packets, following which completed packets are separated fromthe advancing web of sheet material by cutting along a cut line betweenthe transverse edge seal 48 of one packet and seal 47 of the contiguouspacket. However, the space between seals 49 a ₁ and 49 a ₂ has thefurther advantage of permitting a packaging line operator to determinewhether any of the package components are being deposited on the innersurface of the panels 41 and 42 in the region of the inner frangibleseal 49 a, which can impair proper sealing of the panels to each other.This is accomplished by cutting a completed package along the unsealedregion between the two frangible seals 49 a ₁ and 49 a ₂ to check forfluid present therein.

As can be seen in FIG. 8, the opposing panels 41 and 42 are sealed toeach other only in the regions which do not have resist material appliedto panel 41. Thus, fluid can flow through the spaces between the sealedregions in order to fill the converging pockets 61 as previouslydescribed.

FIGS. 9 through 12 show various alternative seal patterns in accordancewith the present invention. In these figures, the patterns are not shownin reverse or negative image, but rather the lines represent the seallines between the opposing panels 41 and 42 of the packet 40. The sealpattern need not be an orthogonal grid as shown in FIGS. 5 and 6, andvarious non-orthogonal grids may be used, such as the one shown in FIG.6 in which intersecting continuous lines 70 form a diamond-shaped gridwith converging pockets 71.

Furthermore, the seal pattern need not be an intersecting or gridpattern. For example, FIGS. 10 and 11 depict two alternative sealpatterns in which continuous lines 80 and 85 extend throughout thefrangible seals 49 a and 46 a. As shown in FIG. 10, the seal pattern isa running W or saw tooth pattern, and as depicted in FIG. 11, the sealpattern is a wavy or sine-wave type pattern. The lines 80 defineconverging pockets 81 and the lines 85 define converging pockets 86.

The seal lines forming the seal pattern need not be completelycontinuous throughout the frangible seals 49 a and 46 a. For example,FIG. 12 depicts a diamond grid pattern made up of lines 90 which havediscontinuities or gaps 91 therein. The gaps 91 are sufficiently narrowsuch that the fluid is prevented from migrating through the seal.

The seal pattern need not be composed of lines or line segments. Forexample, FIG. 13 depicts a seal pattern in which discreet sealed regions95 are spaced apart and surrounded by unsealed areas 96 and are arrangedin a matrix configuration. The matrix is shown as having a substantiallyregular or uniform spacing of the matrix rows and columns butnon-uniform matrixes may be used if desired; for example, for providingrelatively weaker and stronger regions of a given seal.

Where the seal pattern of FIG. 13 is accomplished by applying resistmaterial to the panel 41 or 42 in a reverse image of the pattern of FIG.13, as described above, the resist material advantageously is applied bya half-tone printing process. Half tones are conventionally described interms of half-tone density in lines per inch, each line representing arow or column of the matrix and in terms of percent coverage of thematerial being applied to the sheet. The frangible seals 49 a and 46 amay be formed advantageously by printing resist material in a half-tonematrix having a line density of at least about 15 lines per inch, morepreferably at least about 50 lines per inch, with a coverage of at leastabout 60 percent and more preferably at least about 80 percent.

As stated earlier, where foam precursor components are to be containedin packet 40, it has been found preferable to use a laminant sheet, asgenerally indicated at 120, as is shown in FIG. 15. The laminant sheet120 is formed of five layers. A layer 122 which forms the exteriorsurface of the packet 40 is formed of an orientedpolyethyleneteraphthalate (PET), such as MYLAR. A polyethylene tie layer124 is joined to the PET layer 122, and a metal foil layer 126 is joinedto the tie layer 124. A layer 128 of ethylene acrylic acid is joined tothe inner side of the foil layer 126, and a linear low densitypolyethylene (LLDPE) layer 130 is joined to the layer 128 and forms theinner surface of the packet 40.

The inner layer 130 may also be formed of low density polyethylene(LDPE), other types of polyethylene, and other non-polar polymermaterials, or other heat sealable materials. In printing inks ontonon-polymer materials, it is conventional to treat the surface by way ofcorona discharge or flame treatment in order to modify chemically thesurface to increase the surface energy (measured in dynes) so that theinks adhere more readily to the surface. However, in accordance with thepresent invention, the resist material is applied to the inner surfaceof non-polar polymer material which is in a substantially virgin state,i.e., substantially unmodified by any corona discharge, flame or othertreatment. It has been found that such modifying treatments impair theheat-sealability of the surface, leading to lower-strength permanentseals. Accordingly, the entire inner surfaces of the sheet or sheetsforming the packet 40 comprise substantially virgin non-polar polymermaterial.

Many modifications and other embodiments of the invention will come tomind to one skilled in the art to which this invention pertains havingthe benefit of the teachings presented in the foregoing descriptions andthe associated drawings. Therefore, it is to be understood that theinvention is not to be limited to the specific embodiments disclosed andthat modifications and other embodiments are intended to be includedwithin the scope of the appended claims. Although specific terms areemployed herein, they are used in a generic and descriptive sense onlyand not for purposes of limitation.

1. A packaging system for producing a foam-in-bag cushion upon demandcomprising: a bag formed of flexible plastic film material and definingtherein an enclosed space of a volume corresponding to the size of thefoam cushion to be produced, said enclosed space being vented to theoutside of said bag to permit the escape of gases generated during theformation of the foam cushion while preventing the escape of foamtherefrom; a foam precursor packet positioned at a predeterminedlocation within said enclosed space in said bag and being formed of abarrier material capable of maintaining foam precursor components in arelatively stable and unreacted state, said packet including a firstcompartment and a second compartment with a first frangible sealseparating said first and second compartments and adapted to be rapturedwhen it is desired to form the foam cushion, said packet also includinga second frangible seal between one of said compartments and saidenclosed space in said bag; a first foam precursor component containedin said first compartment of said packet; a second foam precursorcomponent contained in said second compartment of said packet; saidfirst and second foam precursor components being adapted to be mixedupon rupture of said first frangible seal and to react to form foamwhich will rupture said second frangible seal and expand from saidpacket into said enclosed space in said bag until said enclosed space issubstantially filled with foam and said foam cushion is formed; and saidfrangible seals having a peel strength of at least about one-half poundper inch and less than about twelve rounds per inch, wherein saidfrangible seals are each formed by a band of printing extending alongone of the contiguous surfaces of said packet, said band of printingcomprising a pattern of spaced apart printed areas separated by a gridof spaced apart seal lines in orthogonal or non-orthogonal fashionthroughout the length of said frangible seals.
 2. A packaging systemaccording to claim 1 wherein said grid of spaced seal lines are arrangedin a regular matrix having a density of at least about 6 matrix linesper inch.
 3. A packaging system according to claim 2 wherein said matrixhas at least about 50 matrix lines per inch.
 4. A packaging systemaccording to claim 1 wherein said grid of spaced apart seal linesincludes seal lines intersecting at substantially right angles.
 5. Apackaging system according to claim 1 wherein said band of printingcomprises a pattern of printed areas with unprinted areas and whereinsaid printed areas cover at least about 60 percent of the surface areaof said band of printing.
 6. A packaging system according to claim 5wherein said printed areas cover at least about 80 percent of said bandof printing.
 7. A packaging system for producing a foam-in-bag cushionupon demand comprising: a bag formed of flexible plastic film materialand defining therein an enclosed space of a volume corresponding to thesize of the foam cushion to be produced, said enclosed space beingvented to the outside of said bag to pen-nit the escape of gasesgenerated during the formation of the foam cushion while preventing theescape of foam therefrom, a foam precursor racket positioned at apredetermined location within said enclosed space in said bag and beingformed of a barrier material capable of maintaining foam precursorcomponents in a relatively stable and unreacted state, said packetincluding a first compartment and a second compartment with a firstfrangible seal separating said first and second compartments and adaptedto be raptured when it is desired to form the foam cushion, said packetalso including a second frangible seal between one of said compartmentsand said enclosed space in said bag, a first foam precursor componentcontained in said first compartment of said packet, a second foamprecursor component contained in said second compartment of said packet,said first and second foam precursor components being adapted to bemixed upon rupture of said first frangible seal and to react to formfoam which will rupture said second frangible seal and expand from saidpacket into said enclosed space in said bag until said enclosed space issubstantially filled with foam and said foam cushion is formed, and saidfrangible seals having a reel strength of at least about one-half poundper inch and less than about twelve pounds per inch, wherein said firstfrangible seal comprises a pair of spaced apart seals separated by anunsealed region.
 8. A packaging system according to claim 7 wherein saidsecond frangible seal comprises a pair of spaced apart seals separatedby an unsealed region.